const CRC_TABLE: [u16; 256] = [
    0x0000, 0x365E, 0x6CBC, 0x5AE2, 0xD978, 0xEF26, 0xB5C4, 0x839A, 0xFF89, 0xC9D7, 0x9335, 0xA56B,
    0x26F1, 0x10AF, 0x4A4D, 0x7C13, 0xB26B, 0x8435, 0xDED7, 0xE889, 0x6B13, 0x5D4D, 0x07AF, 0x31F1,
    0x4DE2, 0x7BBC, 0x215E, 0x1700, 0x949A, 0xA2C4, 0xF826, 0xCE78, 0x29AF, 0x1FF1, 0x4513, 0x734D,
    0xF0D7, 0xC689, 0x9C6B, 0xAA35, 0xD626, 0xE078, 0xBA9A, 0x8CC4, 0x0F5E, 0x3900, 0x63E2, 0x55BC,
    0x9BC4, 0xAD9A, 0xF778, 0xC126, 0x42BC, 0x74E2, 0x2E00, 0x185E, 0x644D, 0x5213, 0x08F1, 0x3EAF,
    0xBD35, 0x8B6B, 0xD189, 0xE7D7, 0x535E, 0x6500, 0x3FE2, 0x09BC, 0x8A26, 0xBC78, 0xE69A, 0xD0C4,
    0xACD7, 0x9A89, 0xC06B, 0xF635, 0x75AF, 0x43F1, 0x1913, 0x2F4D, 0xE135, 0xD76B, 0x8D89, 0xBBD7,
    0x384D, 0x0E13, 0x54F1, 0x62AF, 0x1EBC, 0x28E2, 0x7200, 0x445E, 0xC7C4, 0xF19A, 0xAB78, 0x9D26,
    0x7AF1, 0x4CAF, 0x164D, 0x2013, 0xA389, 0x95D7, 0xCF35, 0xF96B, 0x8578, 0xB326, 0xE9C4, 0xDF9A,
    0x5C00, 0x6A5E, 0x30BC, 0x06E2, 0xC89A, 0xFEC4, 0xA426, 0x9278, 0x11E2, 0x27BC, 0x7D5E, 0x4B00,
    0x3713, 0x014D, 0x5BAF, 0x6DF1, 0xEE6B, 0xD835, 0x82D7, 0xB489, 0xA6BC, 0x90E2, 0xCA00, 0xFC5E,
    0x7FC4, 0x499A, 0x1378, 0x2526, 0x5935, 0x6F6B, 0x3589, 0x03D7, 0x804D, 0xB613, 0xECF1, 0xDAAF,
    0x14D7, 0x2289, 0x786B, 0x4E35, 0xCDAF, 0xFBF1, 0xA113, 0x974D, 0xEB5E, 0xDD00, 0x87E2, 0xB1BC,
    0x3226, 0x0478, 0x5E9A, 0x68C4, 0x8F13, 0xB94D, 0xE3AF, 0xD5F1, 0x566B, 0x6035, 0x3AD7, 0x0C89,
    0x709A, 0x46C4, 0x1C26, 0x2A78, 0xA9E2, 0x9FBC, 0xC55E, 0xF300, 0x3D78, 0x0B26, 0x51C4, 0x679A,
    0xE400, 0xD25E, 0x88BC, 0xBEE2, 0xC2F1, 0xF4AF, 0xAE4D, 0x9813, 0x1B89, 0x2DD7, 0x7735, 0x416B,
    0xF5E2, 0xC3BC, 0x995E, 0xAF00, 0x2C9A, 0x1AC4, 0x4026, 0x7678, 0x0A6B, 0x3C35, 0x66D7, 0x5089,
    0xD313, 0xE54D, 0xBFAF, 0x89F1, 0x4789, 0x71D7, 0x2B35, 0x1D6B, 0x9EF1, 0xA8AF, 0xF24D, 0xC413,
    0xB800, 0x8E5E, 0xD4BC, 0xE2E2, 0x6178, 0x5726, 0x0DC4, 0x3B9A, 0xDC4D, 0xEA13, 0xB0F1, 0x86AF,
    0x0535, 0x336B, 0x6989, 0x5FD7, 0x23C4, 0x159A, 0x4F78, 0x7926, 0xFABC, 0xCCE2, 0x9600, 0xA05E,
    0x6E26, 0x5878, 0x029A, 0x34C4, 0xB75E, 0x8100, 0xDBE2, 0xEDBC, 0x91AF, 0xA7F1, 0xFD13, 0xCB4D,
    0x48D7, 0x7E89, 0x246B, 0x1235,
];

const CRC_OF_0564: u16 = 0x3F0D;

pub(crate) fn calc_crc(slice: &[u8]) -> u16 {
    !crc_increment(0, slice)
}

pub(crate) fn calc_crc_with_0564(slice: &[u8]) -> u16 {
    !crc_increment(CRC_OF_0564, slice)
}

pub(crate) fn crc_increment(mut acc: u16, slice: &[u8]) -> u16 {
    for byte in slice {
        let index = ((acc as u8) ^ *byte) as usize;
        acc = CRC_TABLE[index] ^ (acc >> 8)
    }
    acc
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn has_correct_constant_crc() {
        assert_eq!(crc_increment(0, &[0x05, 0x64]), CRC_OF_0564);
    }

    #[test]
    fn crc_works() {
        let bytes: [u8; 8] = [0x05, 0x64, 0x05, 0xC0, 0x01, 0x00, 0x00, 0x04];
        assert_eq!(calc_crc(&bytes), 0x21E9);
    }
}
